The invention relates to delivery catheters for delivering and deploying an endoluminal implant to a remote site within a body lumen.
It has long been accepted medical practice to treat a variety of vascular disorders in a surgical procedure that involves surgical exposure of the portion of the patient""s vascular system to be treated and placement of a vascular graft at that site. In order to reduce the risks inherent in such surgery, various devices and techniques for advancing and deploying a vascular graft without requiring a full surgical procedure have been under development. Among those techniques is to provide a tubular implant assembly that can be radially contracted to a low profile (small effective cross-sectional diameter) and loaded into a delivery catheter to enable the catheter to be advanced through the patient""s vasculature to deliver and deploy the implant at its intended site of placement. When located at the intended deployment site, the catheter is operated to eject the implant so that it can deploy to its radially expanded configuration in engagement with the inner surface of the blood vessel.
Among the difficulties presented in such endoluminal placement of an implant is that the implant and catheter are not directly visible to the physician. Therefore, in order for the physician to determine the location of the catheter and the implant, as well as its position within the blood vessel, fluoroscopic techniques are used. Radiopaque elements may be provided on one or both of the implant and delivery catheter. Additionally, radiopaque contrast liquid may be injected into the blood vessel. However, even if the predeployment position of the implant appears to be satisfactory, further manipulation of the delivery catheter in order to deploy the implant, may result in shifting of the graft and misplacement either as to its location, orientation or both.
European patent applications Ser. No. 94116805.6 filed Nov. 10, 1994 (Publication No. 0657147) and Ser. No. 95114543.2 filed Sep. 15, 1995 (Publication No. 0701800A1) describe a recapturable prosthetic implant system that includes an implant and a delivery device in which a substantial portion of the implant may be ejected from the delivery device sufficiently to enable determination whether the implant is in its proper location, orientation and of the correct size. The implant and delivery system are configured to enable the implant to be retracted into the delivery device in the event that the location or orientation is improper. With the implant recaptured, the delivery device can be manipulated into the proper position. The implant then can be partially deployed and its position and orientation again determined. When the implant is located as desired, the delivery device is operated to fully release the implant. The construction of the implant is such that it will remain in the deployed position within the blood vessel.
The delivery device is in the form of a catheter having an elongate tubular sheath arranged to contain the implant in its low profile within the distal end of the sheath. The device also includes an elongate positioning member that extends through the sheath and implant and engages with the trailing end of the implant. The positioning member has a hollow lumen adapted to receive a guidewire so that the delivery device can be advanced into and navigated through the patient""s vascular system in an over-the-wire technique. When the delivery system and implant have been advanced to the intended site of deployment, the positioning member is held stationary while the sheath is withdrawn. As the sheath is withdrawn, the implant is progressively exposed and expands radially toward engagement with the wall of the blood vessel.
An end of the implant remains attached to the positioning member and remains so until the sheath has been withdrawn past the connection of the implant, at which point the implant is released. At any time before the point of release, the sheath can be readvanced over the implant to recapture the implant.
The implant, for example, may include a tubular synthetic graft having leading and trailing ends and a resilient, self-expanding anchor assembly, connected to the graft, that is compressible to a low profile and can expand resiliently to an enlarged diameter. The anchor assembly may include an anchor at each end. Each anchor may be formed generally in the configuration of a continuous zigzag wire arranged in a tubular configuration. Portions of the anchors at the opposite ends of the implant are connected to two or more longitudinal struts. The anchors may be provided with one or more radially outward protruding hooks adapted to engage the blood vessel wall under the influence of the resilient anchor to enhance the resistance of the anchor to migration once the graft has been released from the delivery device.
There is some risk that as the deployment of the device approaches its completion, there may be premature accidental release of the implant. It would be desirable, therefore, to provide a means and method by which such accidental premature release could be prevented.
The delivery catheter is provided with a control handle at its proximal end. The handle has movable components connected respectively to the sheath and the positioning member to control their relative longitudinal movement and position. The handle components are arranged to define at least three relative positions of the sheath and positioning member including (1) an implant capture position in which the sheath fully encloses and contains the implant, (2) a further stage of the implant capture state in which the implant is partially deployed from the sheath but in which the trailing end of the implant remains attached to the delivery device, and (3) a release configuration in which the implant has been ejected from the sheath sufficiently to enable it to be freed from the sheath and fully released within the blood vessel. In the illustrative embodiment, the movable parts of the handle include a shifting mechanism that must be operated deliberately by the physician to enable the handle to be manipulated from one position to the other. Thus, the physician can be confident that the implant will not be deployed prematurely and that it will be released only when the physician is satisfied with its placement and position. The device is ergonomic and can be operated entirely by feel. Thus, the physician is relieved of continuous visual checking of the relative positions of the sheath and the positioning member.
It is among the general objects of the invention to provide an improved delivery device and method for an endoluminal implant that enables the implant to be deployed in partial progressive stages.
Another object of the invention is to provide an improved delivery device for an endoluminal implant in which inadvertent release of the implant is avoided.
A further object of the invention is to provide an improved delivery device for an endoluminal implant that facilitates recapture of the implant.
A further object of the invention is to provide a device of the type described that can be operated substantially by feel and without requiring that the physician divert attention from the other aspects of the procedure.